Stump cutter and wood chipper with novel braking mechanism

ABSTRACT

A stump cutter includes an engine and a cutting wheel. A drive assembly is disposed between the engine and the cutting wheel. The drive assembly comprises at least one pulley. The at least one pulley defines a cylindrical recess therein. A drum brake assembly is configured to engage the cylindrical recess of the at least one pulley.

PRIORITY CLAIM

This application is based upon and claims the benefit of provisionalapplication Ser. no. 62/559,960, filed Sep. 18, 2017, which isincorporated fully herein by reference for all purposes.

FIELD OF THE INVENTION

Example embodiments generally relate to stump cutters and wood chippers.

BACKGROUND OF THE INVENTION

Stump cutters, or stump grinders, are used to remove tree stumps,typically by means of teeth on a rotating cutter wheel at a distal endof a grinding arm. The cutter wheel is swept back and forth across atree stump and lowered at each pass until the stump is removed. Thefinal sweeps may be below ground in order to ensure the entire stump hasbeen eliminated. An example embodiment of a stump cutter is shown inU.S. Pat. No. 6,003,570, which is incorporated fully herein by referencefor all purposes.

Similarly, wood chippers are used to reduce plant debris, such as smalltrees, limbs, etc., into smaller chips. The debris is fed into an infeedchute into contact with the chipper disc or drum. The rotating action ofthe disc or drum grinds the plant debris into small chips which are thenejected through a discharge chute.

SUMMARY OF THE INVENTION

According to an example embodiment, a stump cutter includes an engineand a cutting wheel. A drive assembly is disposed between the engine andthe cutting wheel. The drive assembly comprises at least one pulley. Theat least one pulley defines a cylindrical recess therein. A drum brakeassembly is configured to engage the cylindrical recess of the at leastone pulley.

According to another example embodiment, a wood chipper includes anengine and a chipper structure (e.g., a chipper disc or a chipper drum).A drive assembly is disposed between the engine and the chipperstructure. The drive assembly comprises at least one pulley. The atleast one pulley defines a cylindrical recess therein. A drum brakeassembly is configured to engage the cylindrical recess of the at leastone pulley.

According to another example embodiment, a drive assembly includes aninternal combustion engine and a plurality of pulleys operably coupledto the internal combustion engine. At least one pulley of the pluralityof pulleys defines a cylindrical recess. A drum brake assembly having atleast one brake shoe is disposed at least partially in the cylindricalrecess of the at least one pulley so that the at least one brake shoe isconfigured to selectively engage a circumferential surface of thecylindrical recess.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of preferred embodiments in associationwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendeddrawings, in which:

FIG. 1 is a perspective assembly view of a stump cutter assembly inaccordance with an embodiment of the present invention;

FIG. 2 is a partial perspective assembly view of the stump cutterassembly as in FIG. 1;

FIG. 3 is a diagrammatic representation of an electrically actuated drumbrake for use in the stump cutter assembly as in FIG. 1; and

FIG. 4 is a partial perspective assembly view of a wood chipper inaccordance with an embodiment of the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention according to the disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some example embodiments now will be described more fully hereinafterwith reference to the accompanying drawings, in which some, but not allexample embodiments are shown. Indeed, the examples described andpictured herein should not be construed as being limiting as to thescope, applicability, or configuration of the present disclosure. Likereference numerals refer to like elements throughout. As used herein,“operable coupling” should be understood to relate to direct or indirectconnection that, in either case, enables functional interconnection ofcomponents that are operably coupled to each other.

As used herein, terms referring to a direction or a position relative tothe orientation of a stump cutter assembly or a wood chipper, such asbut not limited to “vertical,” “horizontal,” “above,” or “below,” referto directions and relative positions with respect to the stump cutterassembly's and the wood chipper's orientations in their normal intendedoperation, as indicated in FIGS. 1 and 4, respectively.

Further, the term “or” as used in this disclosure and the appendedclaims is intended to mean an inclusive “or” rather than an exclusive“or.” That is, unless specified otherwise, or clear from the context,the phrase “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, the phrase “X employs A or B” issatisfied by any of the following instances: X employs A; X employs B;or X employs both A and B. In addition, the articles “a” and “an” asused in this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromthe context to be directed to a singular form. Throughout thespecification and claims, the following terms take at least the meaningsexplicitly associated herein, unless the context dictates otherwise. Themeanings identified below do not necessarily limit the terms, but merelyprovide illustrative examples for the terms. The meaning of “a,” “an,”and “the” may include plural references, and the meaning of “in” mayinclude “in,” “at,” and/or “on,” unless the context clearly indicatesotherwise. The phrase “in one embodiment,” as used herein does notnecessarily refer to the same embodiment, although it may.

The term “belt” as used herein refers to an element in the form of acontinuous loop that may transfer driving force from one pulley (e.g., asheave or sprocket) to another.

FIGS. 1 and 2 illustrate a stump cutter assembly 100 in accordance withan exemplary embodiment, which is a portion of a stump cutter machine.Stump cutter assembly 100 includes an internal combustion (e.g.,gasoline or diesel) engine 102 that drivingly couples with a cutterwheel 104, comprising teeth 105, through a drive assembly. Stump cutterassembly 100 is typically attached to a boom (not shown) that pivotsabout a first axis that is horizontal when the stump cutter is in itsintended operational orientation. As a result, cutter wheel 104 (whichmay also be referred to as a grinding disc) is raisable and lowerable inorder to adjust the cutter wheel height in relation to the stump to beremoved. In use, cutter wheel 104 is swept laterally across the stumpvia rotation of the boom about a second axis that is perpendicular tothe ground when the stump cutter is in its intended operationalorientation.

In various embodiments, certain components of stump cutter assembly 100remain fixed with respect to the stump cutter base, while othercomponents (e.g., the cutter wheel) are raisable and lowerable withrespect to the base. For example, the engine (particularly in smallermachines) may be mounted on top of the boom so that it raises and lowerswith the boom. In other embodiments, the engine may be mounted to ahorizontal turntable to which the boom is pivotally connected. The stumpcutter base is usually supported by one or more wheels of a wheeledchassis to facilitate movement of the stump cutter from place to place.The base typically includes a chassis, a tank for fuel, and operatorcontrols. See, for example, previously-mentioned U.S. Pat. No. 6,003,570for additional information on various conventional aspects of a stumpcutter machine.

As used herein, “drive assembly” includes components that operablycouple the engine to engine driven components (e.g., the cutter wheel)as well as braking components. The drive assembly of stump cutterassembly 100 includes a first drive shaft 103 (shown in FIG. 1 butexcluded from FIG. 2) that couples engine 102 with a clutch 106. Driveshaft 103 extends from engine 102, through a first hydraulic pump pulley162, through a pulley, or sheave, 108, and into clutch 106. Pump pulley162 couples with the drive shaft a via keyed joint and drives, via ahydraulic pump belt 166, a second hydraulic pump pulley 164 that, inturn, couples with a hydraulic pump 168 for controlling movement of theboom and, in some embodiments, driving the wheels of the base.

Clutch 106 includes a first portion that is rotationally fixed to thedrive shaft (i.e., so that rotational movement of the shaft causesrotational movement of the first portion of the clutch), regardless ofwhether the clutch is engaged, and a second portion that becomesrotationally fixed with the first portion when clutch 106 engages. Thesecond portion is rotationally fixed with sheave 108 so that when theclutch engages, thereby coupling the first portion to the secondportion, engine 102 drives sheave 108. When clutch 106 disengages, thefirst portion decouples from the second portion, and engine 102 becomesdecoupled from sheave 108. Clutch 106 is an electrically actuatedclutch/brake so that, when an operator desires to cause cutter wheel 104to rotate, the operator engages a switch (e.g., a lever on a handle)that closes a circuit, thereby delivering an electric current (e.g.,from an electrical system, such as a 12 VDC system, including a starterbattery) to an electromagnet within the clutch, causing the clutch toengage and thereby delivering rotational energy to sheave 108. When theoperator desires to halt cutter wheel 104, the operator disengages theswitch, thereby removing the electric current from the clutch andcausing clutch 106 to disengage engine 102 from sheave 108 and furtherengaging a brake integrated within clutch 106 that resists therotational inertia of the second portion of the clutch and, thus, sheave108. A suitable clutch for use in this application is available fromOgura Industrial Corp. of Somerset, N.J.

Sheave 108, in turn, drives a larger sheave 110 via a multiple v-belt112 that has a plurality of longitudinal grooves that mate withcircumferential ridges in sheaves 108, 110. A self-centering screw clampbushing 114 extends through a through-hole in sheave 110 and over asecond drive shaft 116, thereby coupling sheave 110 with drive shaft 116so that rotation of the sheave causes corresponding rotation of thedrive shaft. Drive shaft 116 rotates within a pair of pillow blockbearings 118 that mount via bolts to a structural frame 120. Drive shaft116 drives a third drive shaft, or jackshaft, 122 via a belt 124 thattransfers torque between pulleys 126. Pulleys 126 couple to respectivedrive shafts 116, 122 via corresponding taper lock bushings 128. As aresult, each of the pulleys 126 will rotate with the respective shaft towhich it is mounted. Shaft 116 thus drives jackshaft 122 in rotation.Jackshaft 122, in turn, drives cutter wheel 104.

As shown in FIG. 2, a first guard shroud 130 comprises an inner shroudwall 130 a, an outer shroud wall 130 b, a rear shroud wall 130 c, and acurved shroud wall 130 d. Each of shroud walls 130 b, 130 c, and 130 dpreferably comprises through-holes to provide ventilation and dissipateheat. Shroud 130 further covers moving components, including clutch 106,sheaves 108, 110, belt 112, and a portion of drive shaft 116. Similarly,a second shroud 132 (FIG. 1) that covers pulleys 126 and belt 124includes a side wall 132 a, a curved wall 132 b, and an end cap 132 c.

An electrically-actuated drum brake assembly 150 is mounted to a brakemount 152 that is, in turn, mounted to structural frame 120 (e.g., viascrews 154). Drum brake assembly 150 comprises internal componentstypically found in an electric drum brake (e.g., brake shoes 156,springs, backing plate, electromagnetic actuator, actuator arm, etc.).Drum brake assembly 150 is disposed at least partially in a cylindricalrecess in sheave 110. The cylindrical recess of sheave 110 has acylindrical interior surface 158 (FIGS. 1 and 3) that is configured tobe engaged by brake assembly 150 so that sheave 110 acts as a drum forbrake assembly 150. That is, cylindrical interior surface 158 has adiameter such that it is configured to be engaged by at least one ofbrake shoes 156 of drum brake assembly 150 when drum brake assembly 150actuates. When drum brake assembly 150 deactuates, brake shoes 156disengage from cylindrical interior surface 158.

Brake assembly 150 is housed at least partially (and preferablysubstantially entirely) within sheave 110, thereby providing a compactconfiguration in a direction along to the sheave's axis of rotation. Asshown, a plurality of holes 160 may be defined in the side face ofsheave 110 to facilitate dissipation of heat from brake assembly 150. Ina further embodiment, a separate drum mounts to a hollow interior ofsheave 110 so that the drum rotates with the sheave. Thus, if drum brakeassembly 150 stops the drum, sheave 110 correspondingly stops.

As described above, in operation, an operator engages a switch to causeengine 102 to drive cutter wheel 104. The switch closes a circuitbetween the stump cutter's electrical system and clutch 106, therebycausing the clutch to engage. In some embodiments, the switch is a“dead-man's switch” that includes a spring-loaded lever that, whenreleased, interrupts the electrical potential to the clutch, therebydisengaging the clutch and engaging the clutch's integrated brake. Inthis way, the operator must be holding the handle in order to cause thecutter wheel to rotate. When the operator releases the handle, thecutter wheel stops.

Further, when the operator releases the switch, the switch closes acircuit between the electrical system and drum brake assembly 150,thereby causing drum brake assembly 150 to engage with cylindricalsurface 158 of sheave 110. When the operator actuates the switch, theswitch opens the circuit between electrical system and drum brakeassembly 150, thereby causing the drum brake assembly to disengage fromcylindrical interior surface 158 of sheave 110 and allow sheave 110 torotate freely.

FIG. 3 provides shows additional detail regarding the structure of drumbrake assembly 150 and its actuation in accordance with an embodiment ofthe present disclosure. A voltage provided to an electromagnet within anelectromagnetic actuator 202 causes the electromagnet to create amagnetic field, thereby attracting the electromagnet towards aferromagnetic flat interior surface of the drum (in this embodiment, aninterior face 162 (FIG. 1)) that is perpendicular to the cylindricalinterior surface 158. With respect to the orientation in FIG. 3, theelectromagnetic attraction pulls electromagnetic actuator 202 up and outof the page. A brake pad 203, integral to electromagnetic actuator 202and disposed between the electromagnet and the flat interior surface,engages the flat interior surface. Contact friction between the brakepad and the flat interior surface pulls the electromagnetic actuatortangential to the rotational motion of the drum, or sheave 110 (FIG. 1),at its contact interface with the electromagnetic actuator.Electromagnetic actuator 202 slides along a pin 207 at a distal end of acurved actuator arm 204 so that the electromagnetic actuator can slideparallel to the axis of pin 207 (i.e., into and out of the page in FIG.3) with respect to the actuator arm but is otherwise fixed to actuatorarm 204.

A proximal, opposite end of the actuator arm is pivotably attached to abacking plate about a pin 206. The frictional force between theelectromagnetic actuator and the flat interior surface of the drum brakecauses the electromagnetic actuator to move in the direction of thefrictional force and therefore pulls the distal end of the actuator armvia pin 207, thereby pivoting actuator arm 204 about pin 206. Theactuator arm contacts one of brake shoes 156 at a contact interfacebetween the actuator arm and the brake shoe and forces the brake shoetowards and against the drum (i.e., sheave 110 at cylindrical surface158). That is, a top portion 205 of actuator arm 204, extending beyondpin 206 in a direction opposite electromagnetic actuator 202, pivots tocause a side surface of top portion 205 to press against an opposingside portion of brake shoe 156. For example, as actuator arm 204 pivotscounterclockwise in the orientation of FIG. 1, side surface 205 a of topportion 205 presses against opposing side surface 156 a of brake shoe156. When the switch opens the circuit that provides electricalpotential to the electromagnet, an associated one of retraction springs208 pulls the engaged brake shoe from the drum, thereby disengaging thebrake. An adjustment arm 210 and corresponding spring 212 may be used toset a gap between brake shoes 156 and cylindrical surface 158 to ensureproper engagement.

In a further embodiment, the brake is hydraulically actuated. In such anexample, disengagement of the throttle causes pressurized hydraulicfluid to enter into a hydraulic cylinder in the drum brake assembly,which, in turn, acts against the drum brake springs to apply the brakeshoes to cylindrical interior surface 158 (FIG. 1). When the hydraulicpressure is released, the drum brake springs cause the brake shoes todisengage from the interior surface 158.

Referring again to FIGS. 1 and 2, in an embodiment, cutter wheel 104weighs several hundred pounds (e.g., approximately 300 pounds). Thus,the cutter wheel has substantial rotational inertia when rotating atfull speed. In some embodiments, belt 124 is a cog belt and, therefore,cannot slip against pulleys 126. For this reason, and due to the cutterwheel's rotational inertia, abrupt stops can cause wear to the belt.Thus, the amount or degree to which braking force from drum brakeassembly 150 is applied to the drum (i.e., the force of brake shoes 156against interior surface 158) may be varied by the voltage provided tothe electromagnetic actuator in order to alter the abruptness of thestops. In an embodiment, a resistor R (e.g., a 10 ohm or a 15 ohmresistor) is installed in series between the voltage source (e.g., 12VDC source) and brake assembly 150. The resistor lowers the voltageapplied to the brake, thereby reducing the electromagnetic attractionbetween the electromagnetic actuator 202 (FIG. 3) and surface 162. This,in turn, reduces the braking force and, thus, the rate at which thecutter wheel slows. A potentiometer may be used in design of the stumpcutter to provide a variable resistance in order to determine an idealresistance for an ideal stopping rate for a given embodiment.

Referring to FIG. 4, a wood chipper 300 employs a drum brake within asheave in accordance with an embodiment of the present disclosure. Woodchipper 300 includes an engine 302 that drives a rotating chipperimplement, such as a chipper (grinding) disk or a chipper drum. In thiscase, wood chipper 300 is equipped with a chipper disc 304 (shown inpart in phantom in FIG. 4) although embodiments utilizing a chipper drumare also contemplated. The chipper implement is located inside of ahousing 390 and chips wood fed through an infeed chute (on the oppositeside of housing 390 from the side shown in FIG. 4). The chipperimplement blows the wood chips as they are produced out through adischarge chute (partially shown at 392). In this embodiment, dischargechute 392 is rotatable about a vertical axis so that the dischargedirection can be varied as necessary or desired. Wood chipper 300further includes a base 394 that is supported by one or more wheels 396and one or more retractable legs 398. Certain conventional aspects of awood chipper can be understood with reference to U.S. Pat. No. 5,137,219and U.S. Published App. No. 2011/0006142A1, both of which areincorporated fully herein by reference for all purposes.

The drive assembly of wood chipper 300 includes components correspondingto similar drive assembly components of stump cutter assembly 100 (FIG.1). It should therefore be understood that reference numerals beginningwith a ‘3’ should be functionally and structurally similar to those ofthe stump cutter assembly beginning with ‘1’ of matching subsequentnumerals (e.g., sheave 308 is analogous in function and structure tosheave 108 above). Therefore, the discussion of the components withrespect to the stump cutter is incorporated by reference for thedisclosure of the wood chipper.

Engine 302 couples with a clutch 306 via a drive shaft (not shown) thatextends from engine 302 through a first hydraulic pump pulley 362,through a sheave 308, and into clutch 306. Pump pulley 362 is connected,via a belt 366, to a second hydraulic pump pulley 364 that, in turncouples with a hydraulic pump (e.g., for driving feed wheels).

Similar to the stump cutter embodiment described above, sheave 308drives a larger sheave 310 via a multiple v-belt (not shown) that has aplurality longitudinal grooves that mate with circumferential ridges insheaves 308, 310. A self-centering screw clamp bushing 314 extendsthrough a through-hole in sheave 310 and over a jackshaft 316, therebycoupling sheave 310 with jackshaft 316 so that rotation of the sheavecauses corresponding rotation of the jackshaft. Jackshaft 316 coupleswith the chipper disk 304 via a keyed joint. A guard shroud 330 covers aplurality of moving components.

An electrically-actuated drum brake assembly 350 mounts to a brake mount352 that, in turn, mounts to a structural frame 320. Drum brake assembly350 comprises typical components found in an electric drum brake (e.g.,brake shoes 356, springs, backing plate, electromagnetic actuator,actuator arm etc.) except for the drum itself. Drum brake assembly 350is disposed at least partially in a cylindrical recess in sheave 310.The cylindrical recess of sheave 310 has a cylindrical interior surfacethat acts as an engagement surface of a drum to engage drum brakeassembly 350, as explained in detail above for the stump cutterembodiment. Actuation of brake assembly 350 is otherwise similar tobrake assembly 150 described above.

While one or more preferred embodiments of the invention are describedabove, it should be appreciated by those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope and spirit thereof. For example, whilethe disclosed embodiments are directed to use with a stump cutter with adirect drive from a combustion engine, the various embodiments could bemodified for use with hydraulic or electric motors. Accordingly, itshould be understood that the elements of one embodiment may be combinedwith another embodiment to create a still further embodiment. It isintended that the present invention cover such modifications andvariations as come within the scope and spirit of the presentdisclosure, the appended claims, and their equivalents.

The following is claimed:
 1. A stump cutter comprising: an engine havingan output shaft; a cutting wheel; a drive assembly between the engineand the cutting wheel, wherein the drive assembly comprises a firstpulley and a second pulley and a first belt engaging an outer surface ofsaid second pulley so as to be in driving relationship therewith, andwherein the second pulley defines a cylindrical recess therein having acylindrical interior surface that is radially inward of the outersurface engaged by the first belt and wherein the first pulley isattached to the output shaft of the engine by a clutch and wherein saidsecond pulley being connected to said first pulley by said first belt soas to be rotatably driven by the first pulley; and a drum brake assemblyconfigured to engage the cylindrical interior surface of the cylindricalrecess of the at least one pulley.
 2. The stump cutter of claim 1,further comprising: a third pulley mounted on a common shaft with saidsecond pulley; a fourth pulley mounted on a common shaft with thecutting wheel; and a second belt interconnecting said third pulley andfourth pulley so that said second pulley will rotatably drive saidfourth pulley.
 3. The stump cutter of claim 1, wherein the drum brakeassembly is electrically actuated.
 4. The stump cutter of claim 3,further comprising a switch and wherein the drum brake assembly includesan electromagnet and further wherein at least one brake shoe isconfigured to engage the circumferential surface of the cylindricalrecess upon a closing of the switch that provides an electrical currentto the electromagnet in the drum brake assembly.
 5. The stump cutter ofclaim 4, further comprising a resistance in series with the switch andthe electromagnet, wherein the resistance is selected to reduce abraking force of the drum brake assembly from the braking force absent avoltage drop across the resistor.
 6. The stump cutter of claim 3,wherein at least one brake shoe comprises a pair of brake shoes.
 7. Thedrive assembly of claim 1, further comprising a spring-loaded switchthat is configured to actuate the drum brake assembly brake when thespring-loaded switch is released by an operator.
 8. The stump cutter ofclaim 1, wherein said engine comprises an internal combustion engine.